These are mushrooms that react to stimuli.
What?
This was an interactive installation set up at the Karnaval Humanitaire's stand at the 2010 edition of Lyon's "Fete Des Lumières".
It was composed of a bunch of translucent papier-machè mushrooms that react to different stimuly by lighting up in various colours. Some of the mushrooms would react to distance (using a pair of ultrasound distance sensors), and some would react to alcohol (using ethanol-gas sensors).
How does it work?
I'll write this up in more detail, but these are analog sensors being processed by an Atmega8, that forwards their values to a linux box over RS232. The linux box then runs a python script that calculates light output values and sends those over DMX to a DMX dimmer using a USB DMX Pro. This dimmer then dims some 60W incadescent lightbulbs covered with gels.You can get source code for the project here, which also includes a small python module to easily interface with the USB DMX Pro. This code is in shambles, but also includes the code for the Atmega8, which is just generic ADC->UART code that works quite well.